Closures or caps for containers are used in a vast array of applications in immense quantities. As such, manufacture of these caps must be done in large quantities, and at high speeds, to maintain the relatively low cost of such closures.
Nevertheless, if one were to inspect such closures with a view toward the details thereof, one would recognize that these closures are highly engineered items. As such, tolerances for, for example, threading, internal diameter, cap depth and the like must be maintained in accordance with very strict standards and ranges.
In order to manufacturer closures in a cost-effective manner, many forming or molding apparatuses are configured to mold multiple caps in a single pass or operation of the apparatus. It is not uncommon for these apparatuses to mold as many as 128 closures in a single operation of the molding device.
Although there are numerous arrangements that are employed for closure molding apparatuses, it has been found that in an efficient molding apparatus the closures are molded in a horizontally-oriented manner. That is, the closures are molded with the top wall of the closure lying in a vertical plane. In this manner, the molding apparatus can be assembled to carry out the multiple molding operation in an efficient and cost effective manner, and to provide a machine that can be used in a relatively small physical plant location.
Those familiar with high speed, mass production injection molding will recognize that the closure, like many molded parts, must be ejected from the mold after it is formed. Ejection is typically carried out in a timed manner so that the part has had sufficient time to set to reduce part deformation. However, allowing the part to set too long in the mold block also has its drawbacks. First, the part may have become too rigid to eject without damaging portions or areas of the part, such as threads. Second, permitting the part to set too long reduces the time that the particular mold can be used to form a subsequent part, thus decreasing the machine's production time.
To this end, known injection molding devices include a mold block that is timed to separate to release the closure from the mold. Mold block opening is timed so that the molded part has sufficient time to set, without becoming too rigid, while making efficient use of the mold block. In this manner, the mold block portions reciprocate relative to one another to open, for releasing or ejecting the molded part.
A typical mold may include a cavity portion forming the outer surfaces of the closure and a core portion inserted into the cavity to form the inner closure surfaces and the container-engaging portions, such as threads and the like. In such an arrangement, a knock-out pin reciprocates through the core to eject or dislodge the closure therefrom as the mold portions separate from one another. It has, however, been observed that when the closure is ejected from the core, it can immediately fall away from the separating mold portions. When this happens, the closure can inadvertently fall into areas of the molding apparatus, such as a mold separating drive area, and become lodged in these undesirable areas. As a result, the molding apparatus must be shut down and the closure removed so that the apparatus can be restored to operation.
Accordingly, there exists a need for a cost-effective closure retention arrangement that is easily adapted for use in a high speed injection molding apparatus that prevents early or premature dislodging of the closure from the core plug. Desirably, such a retention arrangement is relatively inexpensive to incorporate into the closure and injection molding device, and does not adversely effect the ability to operate such an apparatus in a cost effectively manner to mass produce closures. Desirably, such a retention arrangement is adaptable for use in all types of closures including threaded closures, bayonet-mount closures and snap-type closures as well as a variety of sizes of such closures.